dm thin metadata: fix __udivdi3 undefined on 32-bit

sector_div() is only viable for use with sector_t.
dm_block_t is typedef'd to uint64_t -- so use div_u64() instead.

Fixes: 3ab9182 ("dm thin metadata: try to avoid ever aborting transactions")
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

drivers/md/dm-thin-metadata.c

@@ -832,10 +832,8 @@ static void __set_metadata_reserve(struct dm_pool_metadata *pmd)
 	if (r) {
 		DMERR("could not get size of metadata device");
 		pmd->metadata_reserve = max_blocks;
-	} else {
-		sector_div(total, 10);
-		pmd->metadata_reserve = min(max_blocks, total);
-	}
+	} else
+		pmd->metadata_reserve = min(max_blocks, div_u64(total, 10));
 }
 
 struct dm_pool_metadata *dm_pool_metadata_open(struct block_device *bdev,